Machine for flexing sheet abrasives



April l2, 1932.

April 12, 1932. Q H ERBY 1,854,021

MACHINE FOR FLEXING SHEET ABRASIVES Filed July 11,11950 3 Sheetsf-Shepl2 April 12, 1932. C, H, DERBY 1,854,021

MACHINE FOR FLEXING SHEET ABRASIVES Filed July ll, 1950 3 Sheets-Sheet 3ATTDRNELI:

Patented Apr. `12, 19,32

UNITED STATES PATENT oFFicE CHARLES H. DERBY, OF MELROSE. MASSACHUSETTS,ASSIGNO-R, BY MESNE ASSIGN- MENTS, TO UNION SANDIAPER COMPANY, OFBOSTON, MASSACHUSETTS, A COR-A PORATION OF MASSACHUSETTS MACHINE EonELEXING SHEET ABnasIvEs Application led. July 11,

The invention relates to a machine for flexing sheet abrasives of thetype having a paper or cloth backing to which the abrasive is bonded byan abrasive binder such as glue.

M The Hexing ofthe abrasive sheet is for the v advantages to be derivedfrom an initially flexed or preformed abrasive sheet. As recited in saidpatent the initial flexing or preforming of the sheet is obtainedthrough fracturing the binder by minute cracks relatively close togetherwith extension generally crosswise the sheet.

The object of the invention is to provide a machine automatic in itsoperation and capable of treating an abrasive sheet by im* parting todeterminate or localized portions thereof the desired convexity orconcavity, or combination of both, and this through an application ofvaried and predetermined pressures.

The invention can best be seen and understood by reference to thedrawings in which- Figure 1 is a plan of the machine.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 shows the machine in front elevation.

- Fig. 4 is a diagrammatic plan of the electrical connections incidentto the machine.

Fig. 5 is a side elevation of an abrasive sheet flexed by the operationof the machine.

Fig. 6 shows in combined section and side elevation a modified type ofthe machine, and

Fig. 7 is a side elevation of an abrasive sheet flexed by the modiedtype of machine shown in Fig. 6.

Referring to the drawings 1 represents the bed of the machine. Bolted tothe bed are spaced. uprights 2, 2 each having a vertical way 3 in it andwhich way isupen on the inner Side of the upright. The

1930. serial No. 467,351'.

uprights are connected by a cross bar 4bolted to their tops.

Mounted to turn between the uprights are flexing rolls 5, 6,respectively. Of these the any suitable source for turning the roll andoperating the machine.

The roll 6, arranged below the roll 5 with bearing against it, is arelatively smalll roll more in the nature of a heavy rod. It ispreferably of steel and its ends are j ournaled to turn in boxes 12, 12slidably contained in the ways of the respective uprights.

The flexing rolls areheld down or maintained in adjusted positionagainstupward movement by means of set screws 14, 1'4 passed through the endsofthe cross bar 4 and bearing at their bottom ends against the boxes 10,10 within which the shaft 9 of the roll 5 turns. The set screws aremaintained in adjusted position by locking nuts 15 thereon turned intolocking engagement with, the ends of the cross bar. The flexing rollsare maintained in position in a manner to permit of pressure beingbrought upon the roll 6 for lifting this roll to bear hard against theroll 5 todistort the rubber face of this `roll asV pressure is applied.To this end there is ar-` ranged below the roll 6 a shaft 16v with'endsturning in boxes 17 .slidably contained in the ways of the respectiveuprights. The shaft 16 bears a set of wheels 18,18 land these wheelshave'peripheral engagement with the flexing roll 6. Below the shaft 16is arrangeda set of toggles. Each of these toggles comprises a knuckle19 to which are hinged links 20, 21. The outer end of the link 20 ofeachvtoggle bears a hub 22 journaled to turn on the shaft 16 While thelink 21 of each Ytoggle bears a hub 23 fixed to a shaft 24 the ends ofwhich turn within boxes 25 at the bottom ends of the ways in therespective uprights. The angular positioning ofthe. links of the .tog-Ygles is such that when the links are angularly bent to a determinateextent the flexing rolls will be maintained in position butsubstantially no pressure will be exerted to press the flexing roll 6against the roll 5. As the toggles are straightened, however, pressurewill be applied to litt the flexing roll 6 hard against the roll 5 andthe amount of this pressure will depend upon the extent that the togglesare straightened.

Pressure is applied to the toggles for straightening them and thepressure is applied and controlled as follows: Inasmuch as the mechanismtor operating the two toggles is precisely alike a description of onewill sutice for both. Lying in front of each toggle and supported bybolting to the bed 1 of the machine is a set of upstanding spacedplates, 31, 32, respectively. These plates form the body of a solenoid33, having a plunger 34 which is secured to the knuckle 19 of thetoggle. Arranged upon the plunger is a coiled spring 35. One end of thisspring bears against the side of the end plate 31 of the solenoid,iitting within a socket 36 therein. The opposite end of the spring bearsagainst a washer 37 on the plunger, and backed by an adjusting nut 38.It is by means of the compression of the spring 35 that force is exertedfor straightening the toggle, and so the amount of force will dependupon the extent that the spring is compressed, while the compression ofthe spring is obtained by the adjustment of the nut 38. In practice itis the adjusted compression of the springs 35, 35 that is relied upon toexert torce for straightening the toggles. This adjustment may be suchthat the toggles will be fully straightened for exerting a maximum forceupon the flexing rolls or a less degree of straightening when less forcewill be exerted. In any event, to prevent the springs forcing the linksof the toggles outwardly into angular positions beyond theirstraightened positions, stops are provided. The stop for each toggle isprovided as follows: Arranged in the end of the air gap of each solenoidbeyond the end of its plunger with threaded extension through the endplate 32 of the solenoid is an adjustable stud 40 with head 41. Havingthreaded connection with the outer end of the plunger with extensionthrough the stud 40 is a bar 42 having a head 43 beyond the head 41 ofthe stud. This headed bar forms a stop for the plunger for as theplunger is thrown forward by the spring 35 for straightening the linksof the toggle the head 43 of the bar 42 will be brought into engagementwith the head 41 of the stud 40 thereby preventing further displacementof the links of the toggle.

The adjustment of the stop bar 42 may be such that its head will engagethe head of the stud just when the links of the toggle are fullystraightened, preventing further movement of the toggle. The adjustmentof the stop bar may however be such that the displacing action o theplunger upon the links of the toggle may be stopped at any determinatepoint short of a complete straightening of the links. In other words, bymeans of the adjustable stop bars 42, 42 for the two plungers the forceexerted by thesprings 35, 35 upon the plungers for straightening thetoggles and raising the liexing roll 6 against the roll 5 may bedetermined with great nicety although the tension of the springs 35, 35may be more than ample to completely straighten the toggles. As aboveexplained however, l prefer that the force exerted by the plungers becontrolled by an adjusted compression of the springs 35, 35 and the stopbars operate as safety devices or preventing any unwarrantedstraightening of the toggles beyond the amount determined upon anddesired.

lhile the torce exerted upon thetoggles for straightening them isexerted by means of the compressed springs 35, 35 the reverse movementof the toggles 'for moving their links into such angluar position as toremove all lifting torce on the ilexing roll 6, is obtained by excitingthe solenoi-ds to pull in their respective plungers. During this actionthe springs 35, 35 will become further compressed, and the power of thesolenoids for withdrawing their respective plungers must'be suiiicientto obtain such further compression of the springs as will enable thetoggles to be thrown into their inactive positions. To intensify theaction on its plunger of each of the solenoids when excited theadjustable stud 40 in the end of the air gap oi each solenoid beyond theend of its plunger, forms a pole piece assisting in the drawing actionupon the plunge-r when the solenoid is excited. The stud is made ofiron. When the plunger is drawn in by the action of the solenoidsupplemented by the action of its pole piece the end of the plungermight contact with the end of the pole piece and, it provision was notmade, the plunger might not be released when the exciting current wascut off from the solenoid due to the residual magnetism which mightreside in the pole piece. To obviate any ditliculty of this kind an airgap 45 is left between the adjacent ends of the plunger and pole piece,and the end of the pole piece is fitted with brass stops 46 againstwhich the end of the plunger will contact when moved inwardly to engagethe stud 40 or pole piece. Owing to the air gap and the tact that littleor no residual magnetism can reside in the brass stops 46 there islittle danger of the plunger being retained by the pole piece, when theexciting current is cut off.

The abrasive sheet 50 is flexed by passage between the flexing rolls 5and 6, and the sheet is ted to pass between these rolls over a table 51arranged fore 'and aftiof the line of contact between them. In orde-rthat the rolls may receive any shape of end cut of the abrasive sheets,that part of the table lying forward of the rolls is provided with rightand left feed guides 52 and 58 respectively, Aby which the abrasivesheets may be properly lined up before being fed to the rolls. Theguides are movable'over the face of the table, andare retained inad]usted position by fastenings 54 which pass through slot 55 in thetable.

TheV application of pressure by the flexing rolls to the abrasive vsheetis automatically controlled as follows: Arranged fore and aft of thecentral line of pressure between the flexing rolls 5 and 6 are springcontacts 56 and 57 respectively. These contacts form a part of anelectricV circuit and each is capable of completing the circuit byengagement with contacts 58 and 59, respectively,` of which the contact58 is arranged in front of the line of pressure between the flexingrolls and the contact 59 back of the line of pressure between the rolls.The contacts 58 and 59 are in the nature of plates extending over thetable and spaced therefrom sufficiently to ensure an easy passage of theabrasive sheet between the plates and the table as the sheet is fed tothe flexing rolls and passed therefrom. The arrangement of theplatecontact 58 is such `that the contact will extend beyond the edge 6l ofthe table lying in front of the flexing rolls while the plate contact 59extends beyond the edge 62 of the table lying back of the flexing rolls.Thus the spring contacts 56, 57 are enabled to have engagement with thecontacts 58, 59 beyond the edges of the table. The contacts have normalengagement with one another and are broken by the abrasive sheet itselfas it is fed passing between the contacts. The distance or amount thatthe ends of the abrasive sheet are flexed is controlled by the adjustedposition of the spring l contacts 56, 57 measured from the central lineof pressure between the flexing rolls. To this end the spring contactsare each mounted upon a support 63 which is adjustable in a way 6l onthe under side of the table and fixed thereto in adjusted position bymeans of a tightening screw 65.

The contacts 56, 58; 57, 59 form a part of the same electric circuit orcontrolling circuit 66 as seen in the diagrammatic plan of Fig.

4. The circuit connecting with the electric source is completed in anysuitable manner as by passage through the machine itself. The circuit iscompleted when either of the spring contacts 56, 57 is touching itscompanion contact 58 or 59 and as explained above, the contacts arenormally in touch with one another, the circuit being broken only by theinterposition of the abrasive sheet as it is fed through both sets ofcontacts simultaneously. It is preferred that an incandescent lamp 67 beplaced within this circuit in order that it maybe noted whether thecircuit is functioning properly.

Connecting with the controlling circuit 66 and having the same electricsource in an operating Vcircuit 70 which connects with the solenoids 33,33 for exciting them when the circuit is closed.` The operating circuitis preferably provided with a rheostat 7lfor standardizing its current.'The operating circuit is closed by exciting the solenoids only when thecontrolling circuit is open. To this end the operating circuit isprovided with a switch 72 controlled by a spring 7 3 forl normallyclosing the switch and closing the circ cuit. i The switch is held openby means of a relay 7 l in the 'controlling circuit, the relay releasingthe switch to close when the controlling circuit is open.

The general opera-tion is as follows: It will first be assumed that thesets of spring contacts 56, 58; 57, 59 respectively, are arrangeddeterminate distances away from the line of pressure between the flexingrolls, the one set in front of the line of pressure and the other setback of the line of pressure. The distances at which these contacts areset with relation to the line of pressure between'the flexing rolls iscommensurate with the extent of flexing of the respective ends of theabrasive sheet. The sheet is then placed upon the table in front of theflexing rolls and so positioned that its front edge will properly feedinto the bight between the rolls. In attaining such position the foreend portion of the sheet will have passed between the contacts 56 and 58breaking the engagement between these contacts.k One or the other of thefeed guides 52 or 53 on the table is vthen set in proper relation to theside edge of the sheet in order that the guide may then be standard forall the sheets subsequently fed. The machine now being in operation, thefore end portion of the sheet will pass between the flexing rolls and beflexed by the operation of these rolls, for at this time the springs 35,35 are operating to straighten the toggles and thereby press the flexingroll 6 hard against the roll 5, thereby flexing the abrasive sheet andfracturing the binder by minute cracks relatively close together withextension relatively crosswise the sheet. The flexing lcontinues alongthe sheet in an amount equal to the distance between the line ofpressure between the flexing rolls and the set of contacts 57, 59 oruntil the fore end of the sheet reaches and passes between the contacts57 and 59, separating these contacts and thereby breaking thecontrolling circuit, for the reason that the body of the sheet is theninterposed between the contacts 56 and 58. With both sets of contactsthus separated and the controlling circuit broken,

the relay 74 will release the switch in the operating circuit to closethis circuit thereby exciting the solenoids. which compress the springsand relieve their tension upon the toggles which are allowed to assumean angular position, thereby relieving the pressure upon the iexing roll6 and accordingly upon the sheet itself. The setting of the parts ispreferably such that the springs will not be so compressed by the actionof the solenoids as to so far bend the toggles that all pressure isreleased from the roll 6 `for flexing the sheet in order that the mainbody of the sheet or that portion thereof lying between its end portionsmay receive some flexing but not the amount of iiexure that the endportions receive. The sheet now progresses until the rear end of thesheet draws out from between the contacts 56 and 58 permitting thesecontacts to have engagement with one another. Thereupon the controllingcircuit will again become completed. rl`he operating circuit will becomebroken through the action of the relay and the solenoids will releasethe springs to act upon the toggles for straightening them and impartingpressure for fiexing the rear end portion of the sheet or that portionlying between the set of contacts 56, 58 and the line of pressurebetween the flexing rolls. Thus the end portions and the intermediateportion of the sheet are flexed, the resulting sheet having a generalconfiguration like that shown diaF gramm'atically in Fig. 5. lf desiredthe machine may be so adjustably set that no flexing of the intermediatebodyportion of the sheet will be obtained, only the end portions.

VIn the machine as above described it will be noted that the abrasiveside of the sheet is in contact with the resilient one of the exingrolls with the effect of imparting convexity to the abrasive sheet, theend portions of the sheet having a pronounced convexity with relation tothe intermediate portion thereof between its ends. If desired thepositioning of the sheet with relation to the resilient roll may bereversed and the abrasive side of the sheet be made to contact with thehard one of the flexing rolls, in which case the same general effect isobtained as before, but instead of a convex sheet there is obtained aconcave sheet.

In Fig. 6 there is shown a further adaptability of the machine in thatprovision is made for making a combination convex and concave sheet suchas that shown in Fig. 7 where the intermediate portion of the sheetbetween its ends is made convex while the ends of the sheet are made tohave a pronounced concavity. lThis effect is obtained by a combinedprimary and secondary flexing mechanism as follows: Associated with amachine of the type just described and arranged in front of the flexingrolls of the machine is another set of flexing rolls 5, 6 of which theroll 5 has a covering of rubber or other resilient material like theroll 5 while the roll 6 is a hard roll like the roll 6. The dispositionof these rolls is such that the resilient roll will lie beneath the hardroll, and the flexing effect is obtained, when the abrasive sheet is runbetween the two rolls, by the weight of a roll 75, made more or lessmassive, upon the roll 6. For supporting the rolls 5, 6 and 75 there isbolted to the bed 1 of the machine spaced uprights 2', 2', each having avertical way 3 in it open on the inner side of the upright, while theuprights are connected by a crossbar 4l bolted to their tops. Theflexing roll 5 is mounted on a shaft 9 which turns within boxes 10', 10contain-ed within the ways of the respective uprights. This roll isextended at one end and bears a driving pulley 11 through which power isapplied for turning the roll. roll 6 arranged above the roll 5 withbearing against it has ends journaled to turn in boxes 12, 12 slidablycontained in the ways of the uprights. The roll arranged above the roll6 with bearing against it is mounted upon a shaft 76 with ends journaledto turn in boxes 77, 77 slidably contained in the ways of the uprights.The roll 75 is held down by means of set screws 14 passed through theends of the crossbar at the top of the uprights and bearing at theirbottom ends against the boxes 77 within which the shaft 76 of the roll75 turns. The screws are maintained in adjusted position each by lockingnut 78 turned into locking engagement with the end of the crossbar. Infront of the set of flexing rolls 5, 6 and leading to the bight of theserolls is a table 51 over which the abrasive sheet is fed. This tablecontinues beyond the rolls and leads to the set of fiexing rolls 5, 6 ofthe secondary flexing mechanism. This secondary flexing mechanism islike that previously described and operates in the same way. Slightstructural differences may be noted between it and the machinepreviously described. The supports 63 carrying the spring contacts 56,57 are arranged in ways upon the cross plates above the table and notupon it as before. The spring contact 56 normally engages an idler roll79 for the abrasive sheet which forms a contact member assisting in thecompletion of the circuit. The spring` contact 57 arranged on the plate59 above the table normally engages the projecting end of the table,which is a little different from the construction previously described.An idler roll 80 for the abrasive sheet is also provided. The flexingroll 5 of the secondary flexing mechanism is preferably driven off theshaft of the liexing roll 5 of the primary flexing mechanism, anysuitable driving mechanism (not shown) connecting the shafts of thesetwo rolls.

In the operation the abrasive sheet is placed on the table in front ofthe rolls 5, 6 of the primary flexing mechanism. This tabl-e is providedwith a set of feed guides the The' rlhe abrasive side of the sheet willthen be in Y contact with the hard one of the flexingrolls. Thesecondary flexing mechanism then functioning as in the machine firstdescribed will tend to further break down the binder at the end portionsof the abrasive sheet and impart a pronounced concavity to these endportions. The secondary flexing mechanism is preferably so set thatlittle or no pressure will be exerted upon the intermediate portion ofthe sheet already flexed by the primary flexing mechanism. The resultingefl'ect is a sheet like that shown in Fig. 7 where, as explained above,the body of the sheet or portion thereof between its end portions isconvex while its end portions have a pronounce-d concavity.

Having thus fully described my invention, I claim and desire to secureby Let-ters Patent of the United States l. An apparatus for flexingabrasive sheets comprising` a set of flexing rolls, means for operatingthe rolls, a set of toggles for applying pressure to the rolls forobtaining the flexing operation by the straightening of said toggles,means for applying pressure to the toggles for straightening themincluding a set of tensioned springs, means for controlling the tensionof said springs, and means limiting the straightening ofk said toggleswhen actuated by said springs.

2. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, means for operating the rolls, mechanism for applying pressure tothe rolls for obtaining the flexing operation and for controlling saidoperation including toggles-7 a tensioned spring for straightening saidtoggles, a bar connecting with the toggles upon which the spring isarranged, a backingfor the spring through which the bar extends, andmeans for ad ustably tensioning said spring.

3. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, means for operating the rolls, mechanismffor applying pressure totherolls for obtaining the flexing operation and for controlling saidoperation including toggles, a tensioned sp ring straightening saidtoggles, a bar connecting with the toggles upon which the spring isarranged, a backing for the spring through which the bar extends, meanson the barvfor tensioning the spring, and means limiting thestraightening of said toggles when actuated by the spring. l 4. AnVapparatus for flexing abrasive sheets comprising a set of flexing rolls,means for operating the rolls, means whereby pressure may be lapplied tothe rolls for obtaining the flexing operation, and mechanism forcontrolling the applied pressure including an electric circuit havingcontacts located at de.- terminate distances forward and back of theline of pressure between said flexing rolls and arranged whereby theymay be severally or together opened by the lsheet to be flexed runbetween said rolls. J 1

5. An apparatus for flexingabrasive sheets comprising a setof flexingrolls, means for operating the rolls, means whereby pressure may be`applied to the rollsfor obtaining the flexing operation, mechanism forcontrolling the applied pressure including an electric circuit havingcontacts located at determinatey distances forward and back of the lineof pressure between said flexing rolls and arranged whereby they may beseverally or together opened by the sheet to be flexed run between'saidrolls, and means whereby said contacts may be set in determinateadjusted positions with relation to saidline of pressurebetween theflexing rolls.

6. An apparatus for flexing abrasive sheets comprising a set offlexingrolls, means for operatingthe rolls, means whereby pressure maybe applied to the rolls for obtaining the flexing operation, andmechanism for controlling the applied pressure including .an electriccircuit having contacts located at determinate distances forward andback of the line of pressure between said flexing rolls and arrangedwhereby they may be severally or together opened by the sheet to beflexed run between said rolls, a solenoid, and means whereby saidsolenoid may be excited when said contacts are opened by said sheet.

7V. An apparatus for exing abrasive sheets lcomprising a set of flexingrolls, 'means for operating the rolls, means whereby pressure may beapplied to the rolls for obtaining the flexing operation, and mechanismfor controlling vthe applied pressure including an electric controllingcircuit and an electric operating circuit, said controlling circuithaving in it contacts v'located at determinate distances forward yandback of the lineof pressure between said flexing rolls and arrangedwhereby they may be severally or together opened by the sheet to beflexed run between saidv rolls and said controlling circuit bebrocircuit is closed and said operating circuit be closed by thebreaking of said controlling circuit. 5

8. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, means for operating the rolls, means whereby pressure may beapplied to the rolls for effecting the flexing operation including adevice tensioned for exerting force, a solenoid having a plunger forrelieving the force exerted by said tension device, and means forexciting said solenoid to relieve the pressure exerted by said tensiondevice including an electric circuit having in its contacts arranged infront of and behind the line of pressure between said flexing rolls andarranged whereby they may be severally or together opened by the sheetto be flexed run between said rolls.

9. An apparatus for flexing abrasive sheets comprising a set of'flexingrolls, means for operating the rolls, mechanism whereby pressure may beapplied to the rolls for obtaining the flexing operation and controllingsaid operation including toggles, a solenoid having a plunger connectedto said toggles, a spring on said plunger, means whereby said spring maybe tensioned to exert force for straightening said toggles and applyingpressure to said rolls or said force be relieved by the exciting of saidsolenoid, and means governed by the sheet itself for exciting saidsolenoid whereby determinate portions of said sheet may be flexed by theoperation of said rolls.

10. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, means for operating the rolls, mechanism whereby pressure may beapplied to the rolls for obtaining the flexing operation and controllingsaid operation including toggles, a solenoid having a plunger connectedto said toggles, a spring on said plunger, means whereby said spring maybe tensioned to exert force for straightening said toggles and applyingpressure to said rolls or said force be relieved by the exciting of saidsolenoid, a pole piece in said solenoid beyond the end of said plunger,a headed rod extending through said pole piece and having threadedconnection with said plunger, and means governed by the sheet itself forexciting said solenoid whereby determinate portions of said sheet may beflexed by the operation of said rolls.

11. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, means for rotating the rolls, means for pushing the rolls closertogether for flexing predetermined portions of the sheet, and means governed by the sheet itself for separating the rolls to relax theirpressure when other portions of the sheet than the predeterminedportions pass between the rolls.

l2. An apparatus for flexing abrasive sheets comprising a set of flexingrolls, meansV for rotating the rolls, means for producing pressurebetween the rolls and controlling the intensity of such pressure, andmeans for confining the pressure on the sheet to prederolls.

CHARLES H. DERBY.

